Genghis khan united the mongols and built an empire by combining

Explanation:

For anyone in UsaTestPrep it is D) a superior cavalry with a confederation of tribes and clans Genghis Khan united the Mongols and built an empire by combining a superior cavalry with a confederation of tribes and clans. Their expertise on horseback allowed them to ride for days at a time and fight with bows and arrows superbly on horseback. Genghis Khan had united the various Mongol tribes in the 1200s, but not along any lines of “racial superiority therefore it is D.

if i am correct the answer is going to be a) the federal program of reconstruction ended.